Hi everyone,
While I'm starting to focus more on node-level optimisations, since they
benefit more platforms and can produce better optimisations in some
situations due to cross-platform support and things like register
allocation, I'm thinking about refactoring and improving x86's
OptPass1MOV routine for the following main reasons:
* It has become a massive, monolithic Frankenstein's monster of an
optmisation routine with lots of different optimisations and styles
of optimisation that are a little difficult to track sometimes (this
is partly a given though since about 25% of all x86 assembly
language consists of a MOV instruction). Some refactoring will make
it more maintainable and potentially faster and smaller.
* It's not as neat and far-reaching as, say, the equivalent routine
for the AArch64 peephole optimizer, which utilises
GetNextInstructionUsingReg that can produce more long-range
optimisations under -O3.
In other news, pure functions are still waiting for some third-party
testing although I've fixed a couple of bugs in the interim. Currently,
the main sticking point are that floating-point values are not being
propagated (pure function analysis utilises constant propagation,
deadstore removal and in-depth node optimisation to calculate output
values). Making a patch to enable this has revealed some shortcomings,
notably how programs and tests behave when floating-point exceptions are
enabled (operations where deterministic values are divided by zero are
being replaced with constants equalling infinity instead of raising an
exception) and also some inconsistent behaviour across platforms where
the Currency type is concerned. Nevertheless, things are coming together.
Kit
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